An analog-to-digital converter (ADC) includes one or more analog stages and one or more digital stages. The analog stage is configured to provide a fixed amount of gain to received analog signals to be converted to digital form. The digital stage, using the known gain of the analog stage, compares the analog signals with known reference voltages, decodes the results, and generates output samples.
Any variation in the amount of gain that is provided by the analog stage can result in errors and/or non-linearity in the samples that are output from the digital stage of the ADC. Unfortunately, gain in the analog stage can vary for a variety of different reasons including temperature, process variations inherent in integrated circuit manufacturing processes, less than ideal performance of electronic components such as amplifiers, and the like.
In some cases, to accommodate for variations in the gain of the analog stage of the ADC, the ADC is taken offline (rendered inoperable) for periods of time during which calibration is performed. The ADC is unusable for the entire time in which calibration is performed. In other cases, changes to the signal path of the ADC, e.g., changes to the capacitive elements in the signal path, are introduced to compensate for gain variation. The changes, however, may not be desirable in terms of overall performance of the ADC.